For this study, Alexandra Zhernakova and her team analysed 1,542 breast milk samples from 524 mothers during the first six months after birth. They examined human milk oligosaccharides (HMOs), special sugars that cannot be digested by the baby but serve as food for beneficial gut bacteria, as well as the bacteria naturally found in milk. They also looked at the mothers’ DNA, the gut microbiota of both mothers and infants, and more than 170 health, lifestyle and dietary characteristics.
A mother’s genetic make-up plays a major role in the composition of her milk. It was already known that genetic factors largely determine the amount of specific HMOs in breast milk, but in the current study the researchers identified a new genetic variant that had not been described before.
They also observed that environment matters: factors such as season of the year, tea consumption and mild breast inflammation were all linked to differences in breast milk composition. Notably, each mother had her own unique milk profile, which remained largely stable, even across multiple pregnancies. However, the composition does adapt to the stage of lactation and the age of the baby.
The new study also showed that breast milk has a direct influence on the early gut microbiota of infants. A few species of milk bacteria survived the journey through the digestive tract and established themselves in the baby’s gut, contributing to the development of their microbiome. Certain sugars were also found to be associated with specific gut bacteria. Although these links were generally small, they highlight the role of breast milk as a unique ecosystem supporting children’s health.
The study’s findings confirm that every mother produces milk that is uniquely tailored to her baby, without the need for supplements or additives. This is an important message, as some commercial parties suggest that breast milk needs to be “enriched”. This study shows instead that every milk profile is valuable. Moreover, the study’s insights can be used to further improve infant formula, so that children who are not breastfed can also benefit from the same key components.
Read the full publication here.
Lifelines NEXT is one of the most extensive mother–child biobanks worldwide, providing a unique opportunity to study the influence of genetics, lifestyle and environment on children’s health. Find more information on Lifelines Next here.
